The climate in the Nile valley used to be as dry as a bone, enabling remarkable preservation of ancient treasures.

But archaeologists believe this is changing and objects and buildings that have survived for thousands of years are threatened with destruction. Malcolm Billings joined a group of Dutch archaeologists at an excavation in the desert at Saqqara, north of Cairo.

That's all we find now instead of wooden objects - just piles of dust. For the archaeologists it's a tragedy

Dr Maartin Raven

The archaeologists took no chances on the perpendicular ladder inside the tomb shaft.

I strapped on a harness and followed Dr Maartin Raven of Leiden Museum down to the main tomb chamber about 20 feet under the surface.

A team of Egyptian workmen were collecting sand in buckets and hoisting them up to the surface.

"This scene hasn't changed in 150 years since people began digging out these tombs looking for treasure," Dr Raven explained. "We still dig with our hands. That way you don't miss anything or damage it."

Tomb raiders

Around us were 20 to 30 crates of skeletons and bits of bone that had come from more burial places in the labyrinth of passages that led off from the bottom of the shaft.

The desert here is a remarkable sight. It's a landscape of humps and bumps and deep pits left by treasure hunters and archaeologists who first explored this place in the 19th Century - the graveyard for the ancient Egyptian capital of Memphis.

Many treasures are on display in Cairo's museum

Archaeologists today don't expect to find anything spectacular. They reckon the tomb-raiders or the early explorers removed everything of value long ago, but they do hope to find out more about the occupants of the tombs.

But in a chapel in a courtyard by the entrance to the tomb they found something stunning. As the archaeologists dug out the sand they found themselves looking into the eyes of two beautifully carved stone figures.

Tombs

It was a double statue, which, according to the inscriptions, were of a high priest and his wife who served the Pharaoh Akenaten in the 14th Century BC.

They still had much of their original paint and there wasn't a scratch on them.

Shawabtis are small statues that answer questions in the afterlife

"They had been sitting where they had been placed, undisturbed for more than 3,000 years," the archaeologist told me.

It was a major find that would be worth a fortune on the illicit art market. The mounted police arrived - on camels - and stood guard until a police escort could be arranged to transport the statue to the Egyptian Museum in Cairo where it is now on display.

The finding of the high priest settled the question of the ownership of the tomb. But where was his coffin? They had carefully searched the chambers and passages below.

Tunnels

Maartin Raven took his torch and led the way on his hands and knees into a labyrinth of tunnels. He pointed up to a concrete pillar they had put in to hold up the roof.

"Sometimes these places collapse," he said in a matter-of-fact tone. "You can't be too careful."

The further we went, the hotter it got, and we huffed and puffed along the passage, stirring up clouds of dust as we went.

The desert is a landscape of humps and bumps and deep pits left by treasure hunters

We stopped at a hole in the side of the tunnel.

"That's the next-door tomb," he said. "We had no idea that it was here, but it's not really a surprise - the rock under the desert here is like miles of Swiss cheese."

Apparently you can get a long way underground following the routes of tomb robbers where they had broken through walls and dug their own access shafts.

I felt that the air was distinctly thin as we scrambled through the hole and into another troglodyte world. A stairway led down into a burial chamber in which we could stand, thank god.

Piles of dust

The archaeologists think this tomb is at least 1,000 years older than the high priest's tomb, but there is no clue as to whose it was and there are no records of anyone having entered it during the past 150 years.

The chamber was empty except for a scatter of bones that would not add up to one skeleton, but nothing else except for a few beads that the tomb robbers had dropped on the way out.

Archaeologists believe that whoever was here in the 19th Century would have found an intact tomb and would probable have left the coffin and the mummy having unwrapped it and taken any jewellery.

There could have been other objects made of wood. The emptiness of these tombs, according to archaeologists, is the result of a change of climate in the Nile Valley.

Since the Aswan Dam was built in the 1950s, the dam has controlled the flooding of the Nile and given farmers year long irrigation.

Dr Raven believes that as a result the fields never dry out. The moisture, he said seeps into the rock under the desert the humidity levels go up and anything organic gradually disintegrates.

"That could have been the high priest's coffin there," he said pointing to some dust on the floor. "That's all we find now instead of wooden objects - just piles of dust. For the archaeologists it's a tragedy."